Short-chained oxygenated VOC (oxVOCs)
emissions from Pinus halepensis saplings were monitored
in response to changes in water availability. Online measurements were made with a proton transfer reaction—
mass spectrometer under controlled conditions, together
with CO2 and H2O exchange measurements. Masses corresponding to methanol and acetone were the most emitted
oxVOCs. All the oxVOC exchanges, except that of acetone
(M59), were signiﬁcantly related to stomatal conductance
and transpiration. Acetaldehyde (M45) emission showed,
moreover, a strong dependence on the concentration of
acetaldehyde in the ambient: stomatal opening (stomatal
conductance above 75 mmol m
-2
s
-1
) only allowed
increased emissions when external concentration were
below 6 ppb. Acetone (M59) presented an important peak
of emission following light and stomatal opening in the
morning when plants were water stressed. Thus, the alterations in oxVOC emissions in P. halepensis caused by the
water deﬁcit seem to be mainly driven by water stress
effect on stomatal closure and oxVOC air concentrations.